Question

Download the file stringB.mat from CANVAS and load it into MATLAB. The file contains a string named stringB. Use MATLAB built-in functions to perform the following exercises.

(a) How many sentences are there in stringB? Put the answer into p4a. Hint: A sentence ends with a period.
(b) Replace all periods in stringB with a backslashes and put the answer into p4b.
(c) Extract the first two sentences in stringB and put them in p4c.
(d) Convert all upper-case letters in string p4c to lower-case and all lower-case letters into upper-case. Put the answer in p4d.
(e-f) Break the two sentences in p4c into two substrings, each with one sentence. Put the answers in p4e and p4f. If the first or the last character in p4e and p4f is either a period or a white space, remove the period or the white space from the answers.
(g) Extract all numbers in stringB and put them in a row vector p4g. The numbers in p4g should appear in the same order as they appear in stringB. Hint: Use strtok to continuously break stringB down into two substrings until it becomes an empty string. At each breakdown, check whether the first substring contains a number. If it is, convert it to

Answer 1

The student's MATLAB questions involve string manipulation and analysis, including counting sentences, replacing characters, extracting substrings, changing letter case, trimming strings, and extracting numbers to create a vector.

Step-by-step explanation:

To answer the student’s question, we’ll assume that the file stringB.mat has already been loaded into the MATLAB workspace and that the variable stringB contains textual data. Below are the steps to perform the requested exercises using MATLAB built-in functions:

1. To count the number of sentences in stringB, which end with a period, you can use: p4a = sum(stringB == '.');

2. To replace all periods in stringB with backslashes, you can use: p4b = replace(stringB, '.', '\');

3. To extract the first two sentences from stringB, first find the indexes of periods: periodIdx = find(stringB == '.'); Then extract the sentences using: p4c = stringB(1:periodIdx(2));

4. To convert uppercase letters to lowercase and vice versa in p4c, use: p4d = swapcase(p4c); where swapcase can be a custom function defined as following: function str = swapcase(s); str = lower(s) + upper(s) - s; end

5. For breaking the string into two substrings each with one sentence, use: p4e = strtrim(p4c(1:periodIdx(1))); p4f = strtrim(p4c(periodIdx(1)+1:periodIdx(2))); The strtrim function will remove any leading and trailing whitespace.

6. To extract numbers, you could iteratively use strtok and isstrprop to check for digits and build the vector: p4g = []; [tok, stringB] = strtok(stringB, {' ', '.', ',','!','…'}); while ~isempty(tok); if any(isstrprop(tok, 'digit')); p4g(end+1) = str2double(tok); end; [tok, stringB] = strtok(stringB, {' ', '.', ',','!','…'}); end;